* it was found that qemu-img rebase could corrupt output images under certain conditions, due to clusters being taken from the backing file rather than the COW file. qemu-image rebase now always gives clusters in the COW file priority over those in the backing file, resolving this issue.(BZ#596378)

* for particular workloads, KVM would become stuck in an infinite loop while updating a guest page table entry (PTE). The qemu process used by qemu-kvm could not be killed, but continues to consume resources. This issue has been resolved. (BZ#596381)

* a rare theoretical race condition was found in the pvclock code for setting the wallclock. An unprotected global variable was used to hold version data, allowing guests to interfere with one another if they would both write wallclock data at the same time. The race condition has been removed, and this issue is now resolved. (BZ#596625)

* an error in a rarely used code path in the refcount table growth code ofqcow2 caused inconsistencies in the metadata, which could lead to real datacorruption later on. The corruption after refblock allocation was fixed,and this issue is now resolved. (BZ#602363)

* after saving a guest snapshot and restarting it, guests failed to bootand suffered a kernel panic. This issue only occurred when guests used virtio block drivers and ran multiple requests at the same time. The qcow2 block driver lacked a synchronous version, which has been added, and the issue is now resolved. (BZ#604188)

All KVM users should upgrade to these updated packages, which containbackported patches to resolve these issues.

Solution

Before applying this update, make sure all previously-released erratarelevant to your system have been applied.